Windows 7, which is currently the world's number one operating system with a market share of more than 50 percent (which means that 1 in 2 PCs are running it), will reach its own end of support on January 14, 2020. As of that moment, Windows 7 will no longer receive updates and security patches, becoming just a product to avoid, as it's the case of Windows XP right now.
The problem is that Windows 7 is growing at such a fast pace these days that it's very likely to become the new Windows XP in 2020 when it's supposed to be killed.